This invention relates to automotive electrical systems and, in particular, to electrical circuitry to control the headlights of an automobile in both day and night conditions.
For many years it has been recognized that a vehicle operating with its headlights on during the day is more easily seen by drivers of other vehicles. Greater visability is thought to reduce the likelihood of accidents. Accordingly, a number of drivers, with a view to that advantage, turn their headlights on during the day.
However, there have been perceived disadvantages concomitant with the use of headlights during the day. For example, at full power, headlights draw considerable energy from the car. Gas must be burnt to generate power to operate them or power must be drawn from the battery. Therefore, a car with headlights on will have a lower gas mileage rating than a car with headlights off. Moreover, the life of the headlight filaments is reduced. There is also a danger that car headlights may be left on when the car is parked which may drain the battery to the extent that the car will not restart. Even if the car if left idling at low rpm""s, the energy of the requirements of the car, augmented by the requirement to power the headlights, may draw power from the battery. There is also the disadvantage that headlights may cause distracting or disturbing glare for other drivers which may cause them to switch their rearview mirrors to nighttime reduced reflection or to take other actions which may lead to lesser visibility and unsafe conditions.
A need had therefore been perceived to provide for daytime running lights which can operate at reduced glare, with low energy consumption and which are automatically turned on when the engine is running and are automatically turned off when the engine is not running. In this manner the advantages of daytime running lights may be obtained without the disadvantages.
Two patents of interest which have been located by the inventors are Canadian Letters patent No. 1,041,594 which issued Oct. 31, 1978 to Westinghouse Electric Corporation for an invention entitled xe2x80x9cTri-Beam Roadway-Lighting System for Motor Vehiclesxe2x80x9d and Canadian Letters patent No. 932,790 which issued Aug. 28, 1973 to General Motors Corporation for an invention entitled xe2x80x9cVehicle Daytime Running Lightsxe2x80x9d.
Canadian Letters Patent No. 1,041,594 discloses four headlights mounted in paired relationships on the front of a vehicle. The headlight filaments are energized in various combinations to provide a low beam, a mid beam and a high beam lighting mode each of which have light distribution patterns which provide improved illumination of the roadway under various driving and traffic conditions with a minimum of glare. The patent does not, however, disclose a lower intensity daytime running lights mode of illumination. Moreover, there is no provision for automatic turning on of the headlights for daytime operation.
Prior art devices have sought to reduce the intensity of the light output by placing an impedance in series with the headlight filaments. As pointed out in Canadian patent No. 932,790, this solution has the disadvantage that heat is dissipated in the impedance and energy is thereby wasted.
Canadian Letters patent No. 932,790 discloses daytime running lights of lower intensity than the low beam headlight mode of operation. According to the patent, the output from one of the output terminals of the three-phase alternating current generator is half wave rectified and is then supplied to the low beam filaments to provide for the diminished illumination. The disadvantage of the approach suggested by Canadian patent No. 932,790 is that the low beam filaments will always be energized by the output of the generator even when the high beam mode has been selected by the vehicle operator. This results in an unnecesary load on the vehicle""s electrical system.
The present invention attempts to overcome the problems of glare and high energy consumption while providing an apparatus and method for readily connecting the apparatus to conventional headlight systems.
It is therefore an object of the invention to provide a circuit for establishing a daytime running mode of operation of vehicle headlights wherein the intensity of the light output is reduced from that in the normal low beam or high beam modes of operation.
It is another object of this invention to provide such a circuit for establishing a daytime running mode of operation of vehicle headlights without the use of an impedance in series with the headlight filaments.
It is yet a further object of this invention to provide such a circuit wherein the daytime running mode is automatically selected and activated when the vehicle engine is running and the vehicle operator has not selected either the low beam or the high beam mode of operation, and which is not selected or activated otherwise.
It is yet a futher and important object of the invention to provide a circuit for establishing a daytime running mode of operation which can be conveniently manufactured as a unit for easy installation in conventional vehicle headlight systems.
Finally it is an object of this invention to provide an easy method for installing such a circuit with conventional headlight systems.
One aspect of the present invention consists in providing a headlight circuit for a vehicle, said vehicle having an engine and a plurality of headlights including headlight filaments, and wherein the vehicle operator may select a normal mode of operation of said headlights whereby a parallel circuit connection is established between at least two headlight filaments, comprising in combination electrical circuit means for establishing said parallel circuit connection between said headlight filaments, electrical circuit means for establishing a series circuit connection between said headlight filaments, means for detecting when the engine is running, means for detecting when the operator has selected said normal mode of operation of the headlights, electrical circuit means for converting said parallel circuit connection to said series circuit connection when the engine is running and the operator has not selected the normal mode of operation of the headlights, whereby said conversion of said parallel circuit connection to said series circuit connection reduces the current flowing through the headlight filaments and reduces the intensity of the light output from said filaments.
In particular, the circuit according to the invention comprises in combination a headlight circuit for a vehicle having an engine and a plurality of headlights including headlight filaments having first and second contact points between which an electrical potential may be applied to induce said filaments to emit light comprising in combination: means for electrically connecting the first contact point of a first of said filaments to a first contact point of a second of said filaments, means for selectively connecting said first contact points of said first and second filaments to a power source means for electrically connecting a second contact point of said first filament to a point of common electrical potential, means for electrically connecting a second contact point of said second filament to switching means, switching means being adapted to assume a first state establishing an electrical connection to said point of common electrical potential or a second state establishing an electrical connection to said power source, means for detecting when the vehicle engine is running, means for establishing said second state of said switching means only when the engine is running and said first contact points of said first and second filaments are not connected to said power source.
A further aspect of the invention resides in a method for connecting a daytime running light circuit to the headlight system of a vehicle as hereinafter described.